1. Field of the Invention
The present invention relates to a chiral liquid crystal polymer (CLCP) layer or pattern that comprises randomly distributed craters of controlled mean diameter and/or density therein. The layer or pattern can be used as a marking on an article or item for identification and/or authentication purposes by exploiting not only the unique optical properties of the CLCP material but also the unique random distribution of the craters.
2. Discussion of Background Information
Every minute billions of items, services and goods are exchanged between people around the world. Some are immaterial and some are tangible, such as, e.g., pharmaceuticals, luxury goods, cigarettes, wine, olive oil, food or banknotes, used for different purposes such as to cure a disease, to provide pleasant moments, to protect us, to pay for something or simply for eating. Although the majority of said items, services and goods is genuine, there is a small part of them that is fake or counterfeit and even worse, may be toxic, especially in the pharmaceutical field or in the case of alcoholic goods. There is not a single day where there will not be a newspaper article somewhere around the world that reports of corresponding problems. This is becoming an increasingly critical problem for all nations and affects not only the economy (at issue are about hundred billions of diversion and counterfeit products) but unfortunately also affects the health of human beings.
For decades attempts to solve this problem have successfully been made, but unfortunately always only for a limited period of time because counterfeiters which now are also linked to criminal organisations develop and improve their skills in parallel with the evolution of the technology and are able to offer to customers fake or non-genuine products which cannot be distinguished from the genuine products by mere visual inspection. This forces the providers of security solutions to constantly be not only up to date, but to be ahead of the counterfeiters in terms of new security features.
In the early days of the development of security features the simple addition of fluorescent compounds to a specific ink was sufficient and may even today still be sufficient as a first level of protection against counterfeit or fake products. But as is often the case, new fake products with markings which mimic the genuine ones have emerged and make it necessary to develop ever more sophisticated and complex inks to overcome this problem.
Another type of security features which has been in use for the last twenty years or so is based upon the random distribution of particles inside a medium. These security features not only deter the selling of counterfeit products because they are difficult to forge, but also provide the ability to create a unique identifier for the items or goods that comprise these security features.
For example, GB 2324065, the entire disclosure of which is incorporated by reference herein, relates to a code that comprises a two- or three-dimensional plastic matrix having embedded therein randomly-positioned visually distinguishable beads. The position of the beads is read and recorded as an identification code, e.g. by recording the position of a sequence of beads above or below a line representative of the ones and zeros in a binary code. The binary code can be read and stored in a database as an identifier of a banknote. Two or more codes may be used, one hidden and one visible, with both codes being recorded.
GB 2374831, the entire disclosure of which is incorporated by reference herein, relates to a signature obtained with a set of particles having a reflective and/or refractive layer or component which are randomly distributed three-dimensionally in a light transmitting matrix on a substrate to provide a security tag. Light reflection/refraction by the particles generates an optical signature which is interpreted by a reader. The signature, which may include the particle coordinates, may be stored in an encrypted or unencrypted form locally or on a central database. The authenticity of a tag is determined by comparing the signature read from it with previously stored data.
US2005/0239207, the entire disclosure of which is incorporated by reference herein, discloses an authentication system that uses the unique random distribution of an invisible taggant as a “signature” to identify an item. The verification is error tolerant and the taggant is made visible to a camera by special illumination. Inert taggants with no optical activity can also be used and made visible by their thermal properties.
U.S. Pat. No. 8,153,984, the entire disclosure of which is incorporated by reference herein, discloses a security marker material that comprises emissive particles selected from at least two groups with different size distributions. The size distributions satisfy the formulae (x−z)2/(Sx2+Sz2)]½>1 wherein x and z are the volume-weighted mean equivalent-spherical diameters of the two particle distributions and Sx and Sz are the standard deviations of the same two distributions. The emissive materials are placed in or on an item. The emissive materials are excited with electromagnetic radiation in one or more specified spectral bands. The electromagnetic radiation is detected in one or more spectral bands from the emissive materials in an image-wise fashion. The attributes of the image are analyzed and characterized and are compared to authentication criteria to determine the authenticity of the marked item. The distribution of the emissive particles is random.
US 2011/0164748, the entire disclosure of which is incorporated by reference herein, relates to a packaging film which contains pigment particles randomly distributed in a low surface-area density and is used for the authentication of products. An imaging device is used to record a first digital image of a packaged product. The positional coordinates, and optionally the color values, of the pigment particles contained in the packaging film are determined from the digital image by means of a computer program and an identification code is calculated from the coordinate or color values and stored in a database. To authenticate the product at a later time, a second digital image is recorded and a test code is determined and compared with the recorded identification code. The number of particles does not exceed 100 particles per cm2 on the surface of the packaging.
WO 2001/57831, the entire disclosure of which is incorporated by reference herein, discloses a method for reading single volume and non-reproducible identification means in the form of a random distribution of bubbles which are present in a polymeric medium. The method consists in recognizing in two dimensions the internal heterogeneous structure of said identification means (bubbles inside the medium) and in isolating and demonstrating its third dimension, thereby eliminating the risk of imposture. Said characteristic makes it possible to reduce storage volume and the periods of time required for scanning, acquisition and comparison operations performed in such processes.
The random distribution of particles in a medium remains a method which is useful for generating a specific and unique code that helps in the fight against counterfeiters. However, the corresponding techniques are not without drawbacks, especially when a low number of particles which serve as a basis of identification and coding is used. With a low number of particles it is easy to determine the position of each (pigment) particle and then to reproduce its position and also to mimic the pigments that are used to generate the unique code. Of course, one way of avoiding this drawback and to enhance the level of protection is to increase the number of pigments and/or particles used and the complexity thereof, which inevitably has an impact on the cost of such solutions and the complexity of the devices required to detect a high number of particles and to generate the corresponding code.
Another drawback of the existing method of the state of the art is the fact that these techniques are strongly dependent on the nature of the particles and the ability of the device used to generate the code, to determine precisely whether or not the pigments are present or not. Multiple readings of the same sample may sometimes lead to different codes. For example, the medium which contains the particles or the bubbles must not interact therewith, and must be as inert as possible toward the particles in order to obtain from these particles the maximum of information they carry. In other words, the previously described techniques are useful for a first level of protection, with the ability to generate a unique identifier, but are strongly dependent on the nature of the particles or the process for generating the bubbles, may be subject to reproduction and have an impact on the cost of corresponding solutions as soon as they require more materials in the form of a pigment. The CLCP flakes (which are similar to small mirrors) are viewed under specular observation which means that the reading will vary with the observation angle.
There is therefore a need for an improved security feature which provides a higher level of protection (above the first level), is cost effective and still is based on the random distribution of particles or an equivalent thereof for being able to generate a unique code that overcomes the drawbacks of the prior art.
It has surprisingly been found that the drawbacks of the prior art can be overcome by using a particular medium which comprises the equivalent of a random particle distribution and at the same time can also serve as an authentication and security feature.